Encasement for steam pipes or the like and method of making same



Jan. 2l",Y 1958 l. oRoURKE, JR., ErAL 2,820,480 5 ENCASEMENT FOR STEAMPIPEs 0R THE LIKE AND METHOD 0F MAKING SAME Filed Sept. 9, 1955 2Sheets-Sheet'l INVENToRs: INNIS OROURKE,JR. GEORGE SPINTER AGENT Jan.21, 1958 Filed Sept. 9., 1955 l. O'OURKE, JR

ET AL ENCASEMENT FOR STEAM PIPES OR THE LIKE AND METHOD OF MAKING SAME 2sheets-sheet 2 INVENTORS: INNIS OROURKE, JR. GEORGE S. PINTER Waff/W'AGENT United States Patentl O ENCASEMENT FOR STEAM PIPES OR THE LIKE ANDMETHOD OF MAKING SAME Innis ORourke, Jr., Upper Brookville, and GeorgeS. Pinter, New York, N. Y.

Application September 9, 1955, Serial No. 533,350 8 Claims. (Cl. 13S-66)Our present invention relates to a protective jacket or encasement forsteam pipes and similar elongated objects adapted to radiate heatintermittently or at varying rates.

In the jacketing of such objects it is important to provide an envelopeof sufficient mechanical strength, low heat conductivity and a smallthermal coetiicient of expansion, resistant to deterioration whenexposed to the atmosphere and when disposed under ground. The mostsuitable material for this purpose is concrete; it has, accordingly,been customary heretofore to encase a length of steam pipe in a concreteenvelope cast in place. This procedure is time-consuming and thereforeexpensive, especially in congested areas.

It is also known to erect such encasement of concrete or other masonryby assembling on the building site a plurality of preformed tubularsections. With presentday methods of manufacture, however, thesesections can only be produced in relatively short lengths, requiring anexcessive number of field connections.

Another drawback of conventional encasements, Whether preformed or castin place, is that the concrete will easily crack under stresses due tovarying temperature.

It is an object of the present invention to provide a moisture-proofencasement for steam` pipes or the like which can be quickly and easilyinstalled on site in long sections and which is rugged enough towithstand handling and to resist stresses due to active forces as wellas thermal stresses.

A more particular object of my invention is to provide a method of soforming a concrete jacket of the above character on a permanentsupporting core as to allow for subsequent thermal expansion orcontraction of the core and the jacket relative to each other.

Still another object of this invention is to provide a method ofmass-producing a number of precast and prestressed units adapted toserve as individual sections of an envelope for an elongated conduit orthe like.

A feature of our invention resides in the provision of a precast,prestressed tubular concrete member whose prestressing elements projectfrom either or both ends of the member to serve as means for connectingit to a second, similar member.

Another feature of our invention resides in the provision of a tubularcore for the concrete member, this core projecting endwise from themember and being adapted. to be joined, either directly or through theintermediary of an expansion joint, to the projecting core portion of anadjacent member and to form a support for a filling of concrete cast inplace to interconnect the two members.

The above and other objects, features and advantages of the presentinvention will become more fully apparent from the following detaileddescription of certain embodiments, reference being made to theaccompanying drawing in which:

Fig. l is a side elevational view (parts broken away of a precastconcrete member forming part of an encasement according to theinvention; t

Fig. 2 is a sectional view taken on the line 2-2 of Fig. '1;'

Fig. 3 is a perspective view, drawn to a smaller scale, of a corrugatedmetal sheet forming the core for the member of fig. 1;

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Fig. 4 is a greatly enlarged fragmentary sectional view taken on theline 4-4 of Fig. 3;

Figs. 5 and 6 are fragmentary sectional views, similar to part of Fig.2, of two modified precast members embodying the invention;

Fig. 7 is a top plan view of a casting site used in the manufacture of aseries of precast members of the type shown in Fig. 1;

Fig. 8 is a top plan view of a building site, illustrating the jacketingof a conduit by a series of members of the type shown in Figs. l and 7,and

Fig. 9 is a fragmentary view (partly in section) of an expansion jointused in place of one of the joints of Fig. 8.A

The member 10 shown in Figs. l and 2 comprises an inner core 11 ofcorrugated sheet metal and a surrounding concrete layer 12; sheet 11projects at both ends beyond layer 12. An untensioned reinforcement 13,shown as a helical steel spring, and a series of prestressed steeltendons 14, lying along generatrices of a cylinder concentric with core11, are imbedded in layer 12; it will be noted that tendons 14 extendsomewhat beyond the ends 0f core 11. The unit 10 concentrically envelopsa steam pipe 15, leaving a cylindrical air space 16 between the sheet 11and a layer of insulation 17 which sheaths the pipe 15; the properspacing is maintained by a series of segmental supports 18 (only oneshown).

The metal sheet 11 is composed of a plurality of sections 11a, 11b, 11eas shown in Fig. 3. These sections are joined together by circularlydisposed rivets 19', 19"; each section is rolled into a cylinder from aflat sheet whose opposite edges are interconnected by longitudinallydisposed rivets 20a, 2Gb, 20c to form a seam. Each rivet passes throughapertures slightly larger in diameter than the stem of the rivet wherebysome relative motion or breathing of the overlapping sheet portions willbe possible. It will be noted that the seams formed by the rivets 20a,2Gb, 20c are angularly staggered, whereby any relative tangentialmovement of the sheets may occur along the stepped line20a19-20b-19-20c; this movement is restrained by the shearing resistanceof the layer 12 along lines 19 and 19" when the core 11 is encased inconcrete. In the axial direction, on the other hand, such movement isopposed only by the tensile strength of the concrete which might beinsuicient in the absence of prestressing as provided by tendons 14.

The sheet 11 is coated externally with an asphalt layer 21 separatingthe metal from the concrete 12. This bituminous layer, besides servingas a waterproofing agent, has a dual function. On the one hand itprevents any bonding between the metal and the concrete, therebyavoiding the formation of cracks in the shell 12 due to unequalexpansion of the two materials. On the other hand it constitutes ayieldable cushion between the core 11 and the layer 12, thus allowingthe metal to expand without busting the concrete shell. The lattereffect is due not only to a certain mobility of the asphalt layer 21especially when heated, which tends to equalize radial stresses all overthe periphery of core 11, but also to the fact that the seams of thecore are not perfectly fluidtight and form channels through which partof the asphalt will be extruded into the interior of the core, as shown`at 21 in Fig. 4, when the pressure becomes excessive. ASheet 11 isshown provided internally with a heat-reflecting lining 11', e. g. ofpaper-backed aluminum foil.

Although the provision of a permanently imbedded metal core 11 isdesirable to facilitate the assembly on site, as will be apparenthereinafter from the description of Fig. 8, it is to be understood thatother materials may be used to support the concrete. Thus, we have,shown in Fig. 5 a precast member 110 whose concrete.

J layer 112, whichiapart from its square consuraton is.

similar to layer 11, is cast directly on a core 111 of Yfibrousmaterial. While asbestos has been shown as a specific example of mineralfibers, it will -be appreciated that vegetable-or syntheticv fibresifmayvlikewise :be used. The reinforcements 113, 114ofV Fig.` 5correspondto-elements 13 and 14, respectively, ofFig. 1.

The member 210. of Fig. 6 is again similarfftopmember 10, except thatits concrete shell 212t isfseparated from its metallic core 211 by afibrous cushioning `layer 221, e. g. of glass wool.. Shell 212 alsohas.imbedded in it the reinforcements and prestressing `elements 213, 214.

In Fig. 7 we have shown an elongated trough 30 used for producingseveral (here three) precast members k10. Resting on suitable supports(not shown) within the trough are the cores 11 of these members,-surrounded by the prestressing tendons` 14 which are common to all themembers and have their Vterminals secured to a stationary anchor 31 anda movable anchor 32. Anchor 32 is displaced, as indicated'by the arrow,until a de-` sired tension has been imparted to the tendonsv 14; theuntensioned reinforcing coils 13 are wound around these tendons, asshown for the middleunit in Fig. 7. Next, with the aid of form work 33,the shells 12 are cast on the cores 11 which have previously been coatedwith their asphalt layers 21 (Fig. 1). After the concrete has hardened,the tendons 14 are released from their anchors 31, 32 and are cutbetween adjacent` members 10 for easier handling and transportation ofthe latter.

ln Fig. 8 a length of steam pipe 15a, sheathed in insulation 17a, and alength of steam pipe 15b, sheathed in insulation 17b, are interconnectedby an elbow 15C enabling a certain longitudinal expansion of the pipes.Pipe 15a is shown enveloped by a series of precast units A, 10B, 10Cwhose cores 11B, 11C are butt-Welded and Whose prestressing rods 14B,14C are lap-welded as shown; the joint between adjacent units isthencompleted by grouting 34 as-illustrated for the members 10A and 10B.A similar member 10D is shown enveloping the pipe b. It will beunderstood that the encasement of pipes 15a, 15b, 15e` is completed by ajacketing of elbow 15e with the aid of precast and/or poured concrete inthe manner generally described above.

In Fig. 9 two lengths of steam pipe 31511, 315b, welded together attheir ends, are sheathed in respective encasements comprising cores311:1, 311b within precast and prestressed envelopes 310a, 310b,respectively.y The prestressing tendons are cut olfy llush with the faceof envelopes 310e and 310b, beingthus invisible in Fig. 9. Cores311aand-311b, protruding beyond these envelope face are bridged by altubular'shield 335-slipped loosely over th`eir^projecting ends.Preformed disk-like'fllers 336a, 336b ofcompressible-material, e. g.cork, rubber or-asphalt-impregnated fabric, engage the end. faces -ofprecast members 310a, 310b; -these members are provided; neary theirsaidv faces, with peripheral annular grooves 337a, 337b`receivingrubber. gaskets 33811, 338b. Av concrete jacket 334 is cast 'inplaceV without bond around the asphalt-coated extremities of members31011, 310b and around llers 336:1, 336b as well as shield 335 to forman expansion joint enabling limited relative axial movement between thetwoenvelopes 310:1, 311a and 31011, 311b.

It may be mentioned that the formation of precast members of lengthsupto about 40 feet by the herein disclosed methodhas .been foundpractical. The invention is, ofcourse, not limited to thespeciiicembodiments described and illustrated but may be realized inayarietyf of modifications ,and adaptations; without departing from;thegspiritgand scopeof the appended claims.

Weclaim:

1. vThe method-.of jacketing-.an elongated conduit which comprises thesteps-of-'precasting a pluralityof tubular concrete shellsfomrespectivetubular sheet-supportsin suclrmannerAvr as to have each ysupport -1'project endwise beyond itsshell, said supports having an inner diametergreater than the outer diameter of said conduit, axially prestressingeach of said concrete shells, positioning said shells in spacedlocations withV clearance around said conduit, and interconnecting saidshells by pouring tubular concrete links therebetween around saidconduit.

2. The method of jacketing an elongated conduit which comprisesthe stepsof precasting a plurality of tubular concrete shells onrespectivetubular sheet supports in suchy manner as tohave each support projectendwise beyond its shell, said supports having an inner diameter greaterthan the outer diameter of said conduit, embedding elongated, axiallyyextending reinforcements in each of said shells, tensioning saidreinforcements against the concrete, positioning said supports adjacentone another with clearance around said conduit, interconnecting theprojecting ends of adjacent supports, and pouring a connecting layer ofconcrete around said interconnected projecting ends.

3. The method according to claim 2, comprising the further step. ofletting the extremities of said reinforcements project beyond therespective shells and joining together said extremities projecting fromadjacent shells, said supports being interconnected by a permanent bond.

4. The method according to claim 2, wherein said connecting layer isformed as part of an expansion joint interconnecting adjacent shellsWithout bond, said supports being joined together with freedom ofrelative axial movement.

5. A method of forming an insulated length of pipe which comprises thesteps of providing a plurality of pipe sections, encasing each of saidsections with all-around clearance in a slightly shorter, tubular sheetsupport, pouring a layer of concrete around said support, therebyforming a precast shell for each section, axially prestressing saidshell, individually transporting the so encasedsections to a buildingsite, positioning said sections end to end at said building site,joining adjacent sections together at their supports, and pouring linksof concrete between the shells of adjacent sections.

6. An encasement for steam pipes and the like, comprising a tubularsupport of solid sheet metal rolled with overlapping edges forming aperipheral cleavage, a concrete shell carried externally on saidsupport, and a heatsoftenable mass forming an anti-bonding, cushioninglayer between said support and said shell adapted to be extruded throughsaid cleavage upon thermal expansion of said support.

7. vAn encasement according to claim 6, wherein said layer consists of aviscous mass, said support being pro vided with seams forming narrowchannels for the extrusion of said mass -under pressure between saidsupport and said shell.

8. An encasement forsteam pipes and the like, comprising a tubularsupport, a concrete shell carried externally. onY said, support, atubular array of elongated prestressing means in said shell maintainingthe concrete thereofunderaxial compression, untensioned reinforcementmeans extending helically around said prestressing means withinl saidshell,.and an tanti-bonding, cushioning layer between said support andsaid shell.

References Cited in the le of this patent UNITED STATESPATENTS 771,594Wilhelmi Oct. 4, 1904 977,345 Tidnam Nov. 29, 1910 994,200 Riker June 6,1911 1,004,570 Hirsh- Oct. 3, 1911 1,021,082 Wrightet al. Mar. 26, 19121,083,002 Chorls Dec. 30, 19,13 1,771,167 Dolan Iuly'22, 1930 1,774,599Hutchinson Sept. 2, 19,30v 2,153,741 Cobi Apr. 11, 1939 2,355,584Douglas e Aug. 8, 1944` 2,747,249 Chiverton May 29; 1956"

